I pulled the boat yesterday out of the marina for the first time in 6-7 months for a post springer season cleaning. The worst algae growth is within 20" of the waterline where the sunlight reaches.
It is important to wash the boat within 30 minutes of pulling it from the water while the scum is still soft and not dried on. With a broken pressure washer, I am reduced to using soapy water and a 3M scrubby backed sponge.
One pic shows where a few seconds scrubbing easily removed the worst growth from the stern. The lower unit on the big Yamaha was disgustingly thick with green slime. Thanks to last year's application of paste wax on the motor and the annual Shark Hide treatment, I washed and cleaned and had the whole outside hull and top clean and gleaming in under 2 hours. I'll wax the paint and motors and apply some more Shark Hide today or tomorrow.
CW